[MS20] Google OSS-Fuzz integration 2/2

[vy]

In #2891, we delivered the preliminary Google OSS-Fuzz integration for Log4j and Log4cxx projects. During development, we encountered several issues both on our end and on the Google side of things. Such that, some even helped to spot serious problems on the OSS-Fuzz infrastructure. Eventually, we managed to successfully complete the integration of both

• Log4j (log4j2: Switch to the Log4j 2 development branch google/oss-fuzz#12514)
• Log4cxx (apache-logging-log4cxx: Switch to the main branch google/oss-fuzz#12538)

This work was made a part of the associated official projects and this is reflected in their websites:

• Log4j
• Log4cxx

[grobmeier]

Looks good to me, thanks!